A working vehicle driven by a wheel includes an engine, a drive shaft rotated by driving force generated by the engine, and an axle device coupled to the drive shaft. The axle device has an axle housing, a differential, a transmission shaft, and an axle shaft. The differential is housed in an internal space of the axle housing, and is coupled to the drive shaft. Rotating force of the drive shaft is transmitted to the transmission shaft via the differential. Rotating force of the transmission shaft is transmitted to the axle shaft. A machine component of the axle device housed in the internal space of the axle housing is immersed in oil. The wheel of the working vehicle is driven by the rotation of the axle shaft.
The axle device has a sliding portion such as a gear or a bearing. A machine component of the sliding portion is deteriorated due to wear. Therefore, an overhaul of the axle device is performed, and maintenance work of the machine component or replacement work of the machine component is performed.
The overhaul of the axle device is preferable to be performed at appropriate timing. If the overhaul is frequently performed even when the machine component of the axle device is not deteriorated, an operation rate of the working vehicle decreases and cost for the overhaul increases. On the other hand, if the overhaul of the axle device is not performed, progress of wear in the machine component of the axle device or breakage of the component occurs and thus, life of the machine component exhausts before the overhaul is performed. Therefore, it is desirable that the overhaul of the axle device be performed at appropriate timing immediately before the life of the component exhausts while the frequency of the overhaul is suppressed.
Patent Literature 1 discloses a technique for diagnosing a failure of a hydraulic cylinder based on a magnetic body attracted by a magnet.